Antisurge control for refrigeration compressors



Dec. 1, 1953 Filed March 11, 1947 A. H. HEINEMAN 2,661,145

ANTISURGE CONTROL FOR REFRIGERATION COMPRESSORS 2 Sheets-Sheet 1 l hcomvnzs son.

m w R Dec. 1, 1953 A. H. HEINEMAN ANTISURGE CONTROL FOR REFRIGERATION COMPRESSORS Filed March 11, 1947 2 Sheets-Shet 2 Patented Dec. 1, 1953 AN TISURGE CONTROL FOR REFRIGERA- TION COMPRESSORS Arnold H. Heineman, Chicago, Ill., assignor, by mesne assignments, to Guardite Corporation, Wilmington, Del., a Delaware corporation Application March 11, 1947, Serial No. 733,799

4 Claims.

This invention relates to a surge control for centrifugal compressors, and more particularly to a means for automatically preventing surging.

Centrifugal pumps are commonly used for refrigeration compressors, and the like. In the operation of such compressors, the compression ratio, that is, discharge pressure divided by the suction pressure, often reaches such magnitude as to cause the gases undergoing compression to surge back over the blades of the compressor from the discharge side to the suction side of the pump. Such surging causes considerable noise, vibration and materially detracts from the efiicient operation of the machine.

I have invented, and am herein disclosing and claiming a control for centrifugal compressors which will automatically prevent surging by maintaining the compression ratio within predetermined limits. By use of my device, the compression ratio will never exceed a predetermined maximum and the device is operative regardless of discharge or suction pressure, being responsive only to compression ratio.

The invention will be described in conjunction with the drawings, in which Fig. 1 is a schematic drawing of the device; and Figs. 2 and 3 are enlarged detailed views of the control means shown in Fig. 1.

Referring now to the drawing, I indicates a centrifugal compressor having a discharge conduit l I and an intake or suction conduit l2. Bypass means l3 are provided between the discharge and the suction side of the compressor, the bypass being normally closed by valve means :4.

Connected to the discharge side of the compressor by means of a conduit [5 is a regulating means "5. A supply of regulating fluid under pressure (preferably compressed air) is connected to the regulating means by a conduit H. The regulating means l6 may be of any ordinary type capable of preventing flow from the conduit 1! into the conduit l8, but responsive to the pressures in the conduit [5 to permit such flow. As shown in Fig. 2, a valve is mounted on a valve stem 4| which is connected to a diaphragm 42 connected to a rack and pinion device 45 which,

in turn, is connected to an indicating means 46 on the face of the means l6. Regulating fluid, when permitted to pass the regulating means I6, is conducted to a suction control means I9. The pressure of the regulating fluid in the conduit conduit 34 connected to the intake l2.

2 I8 is, of course, adjusted by the regulating means l6 which in turn is responsive to the discharge pressure from the compressor, as just described. A slow bleed [8a of any suitable sort is provided in the line l8, as is customary in such controls, to permit pressure to drop in the line If! after the valve 40 has opened and closed during a control cycle. Also connected to the control means 19 is a source of control fluid under pressure conducted to the control means by the conduit 20. In the drawings, the control fluid and regulating fluid receive their pressure from a single source (not shown) through the conduit 2|, however, it is clear that two separate sources of fluid under pressure may be provided, if desired. The control means H! is constructed somewhat similarly to the regulating means It, it being a device adapted to permit or prohibit control fluid pressure to enter the conduit 22. A suitable means is shown in Fig. 3 in which an air chamber diaphragm 4'! is connected to a valve 48. Regulating fluid pressure in conduit I8 is admitted to one side of the diaphram and suction pressure to the other side by means of Spring means 49 normally maintain the valve operated by the diaphragm in a closed position, the tension of the spring being such that it is overcome by excessive difierences between regulating fluid pressure and suction pressure to open the valve to permit control fluid to pass into the conduit 22. A rack and pinion device 50 is connected to the valve stem 5| and to an indicating means 52 on the face of the means I9. The control means is so adjusted that it will permit the con-. trol fluid to flow through it and, by means of the conduits 23 and 24, to the valve means 25 and 26. The valve means 25 is adapted to open or close a shutter 21 on the suction side of the compressor. A spring 28 normally maintains the valve 21 in closed position as shown, it being understood that the valve is provided with a few holes to permit refrigerant, or whatever gas is being compressed, to flow therethrough to the com pressor even when the valve is fully closed. The pressure of the control fluid passing through the control means l9 and conduits 22 and 23 enters an air chamber 29 on one side of a diaphragm 30. When the pressure in the air chamber is suflicient to overcome the tension of the spring, the valve 2'! will begin to open. In the normal refrigeration compressor, I prefer to have the valve 21 begin to open when the control pressure is in the neighborhood of 2 pounds, it being fully open when the pressure reaches approximately 10 pounds. Control pressure is also supplied by means of conduit 24 to the valve control means 26. This means is constructed to remain closed in normal operation, the valve 3| being held in such closed position by the spring 32. I prefer to choose a spring having a greater resistance than the spring 28, to prevent the valve 3! from opening under lower pressures. In other words, if the first spring 28 is adapted to begin to open at a pressure of 2 pounds, and to be fully opened at a pressure of pounds, I prefer to construct the spring 32 so that the valve 3| will remain fully closed until the pressure reaches 10 pounds, and the valve 31 will become fully opened when the pressure in the air chamber 33 reaches 18 pounds. It can be seen then that the valves 25 and 26 operate in sequence, the valve 25 being opened fully before the valve 26 begins to open. A slow bleed 22a of any suitable sort is provided in the conduit 22 so that when the valve 48 closes pressure may drop in the conduits 23 and 24 to permit valves 21 and 3| to return to their normal positions.

The operation of the device is as follows: the regulating means is preset by the means hereinabove described to prevent regulating fluid from entering the conduit 18 until the discharge pressure has reached a desired minimum amount. As discharge pressure exceeds that amount, regulating fluid is admitted to conduit I8. The control means I9 is adapted to supply control fluid to the conduit 22 when the difference between the pressure of the regulating fluid and the pressure in the suction side of the compressor reaches a predetermined amount. It is evident, then, that the valve means 25 and 26 are called into operation only upon excessive pressure differences, and their control is independent of the actual pressures existing in the discharge conduit H or the suction conduit [2. The opening of the valve means 25 tends to increase the pressure on the suction side of the compressor. If the compression ratio continues to mount after the valve 21 is fully opened, additional control fluid pressure is admitted to the conduits 22 and 24, which additional pressure is sufficient to overcome the spring 32 and open the by-pass valve 3 I. Compressed gases are then by-passed directly to the suction side of the compressor, which immediately decreases the discharge pressure and increases the suction pressure to prevent surging. When pressure drops on the compression side, valve is closed, and control fluid bleeds from the conduit l8 through the bleed 18a to reduce the pressure below the diaphragm 41 in the control unit 19, and at the same time the increased suction pressure raises the pressure above said diaphragm. As the pressure differential on the diaphragm 4! drops the valve 48 closes, and control fluid escapes through the bleed 22a to permit valves 21 and 3| to return to their normal position.

While I have shown and described my invention in its preferred embodiment, it is to be understood that it is capable of many modifications. Changes, therefore, in the construction and arrangement may be made without departing from the spirit and scope of the invention as disclosed in the appended claims.

I claim:

1. In a closed centrifugal compressor system including a compressor having a suction input and a pressure discharge, an anti-surge device comprising: a source of regulating fluid under pressure which is independent of the compressor system; regulating valve means; means connecting said valve means to said source of regulating fiuid and to the compressor discharge whereby said valve means may pass regulating fluid at a pressure which varies within predetermined limits with the discharge pressure; a source of control fluid under pressure; suction pressure control means connected thereto and to the suction input of the compressor and means interconnecting said valve means and said control means, whereby pressure of regulating fluid from said regulating means and pressure dependent on suction pressure jointly cooperate within said control means to allow same to pass control fluid at a pressure which varies directly with changes in the difference between the suction pressure and the pressure of the regulating fluid; and valve means mounted in the suction input and under the control of said suction pressure control means to vary suction pressure directly in response to variations in control fluid pressure.

2. The anti-surge device of claim 1, in which the valve means mounted in the suction input comprises a normally closed suction input valve which allows a predetermined minimum suction pressure when closed, said valve being adapted to be opened in response to pressure of the control fluid.

3. The anti-surge device of claim 1 and additional valve means including a normally closed by-pass valve operatively disposed in a conduit connecting the suction input with the pressure discharge and adapted to be opened in response to increasing pressure of the control fiuid to bypass gas from the discharge side of the compressor to the suction side thereof.

4. In a closed centrifugal compressor system including a compressor having a suction input and a pressure discharge, an antisurge device comprising: a source of regulating fluid under pressure which is independent of the compressor system; regulating valve means; means connecting said valve means to said sourceof regulating fluid and to the compressor discharge "whereby said valve means may pass regulating fluid at a pressure which varies within predetermined limits with the discharge pressure; a source of control fluid under pressure; suction pressure control means connected thereto and to the suction input of the compressor, and means interconnecting said valve means and said control means whereby pressure of regulating fluid from said regulating means and pressure dependent on suction pressure jointly cooperate within said control means to allow same to pass control fluid at a pressure which varies directly with changes in the difference between the suction pressure and the pressure of the regulating fluid; a first normally closed valve in the suction line of the compressor which allows a predetermined minimum suction pressure when closed; and a second normally closed valve operatively disposed in a conduit connecting the suction input with the pressure discharge, each of said valves being under the control of said suction pressure control means to open in response to increasing control fluid pressure.

ARNOLD H. HEDIEMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,154,959 Banner Sept. 28, 1915 1,229,500 Newton June 12, 1917 1,280,811 Moss Oct. 8, 1918 1,830,022 .Fourness Nov. 3, 1931 1,833,064 Baumann Nov. 24, 1931 2,409,533 Borden Oct. 15, 1946 2,470,565 Loss May 1'7, 1949 

